Anaesthesia--breathing apparatus

ABSTRACT

An anaesthesia-breathing apparatus for supplying gas to a patient for artificial respiration, supported respiration, anaesthesia purposes or combinations of such purposes. The apparatus comprises a gas chamber connected to a patient connection piece, a respiratory gas receptacle, for example in the form of a respiration bag, a first check valve adapted to permit discharge of excess gas from the breathing apparatus to the atmosphere and, optionally a filter for absorption of carbon dioxide from recirculation breathing gas. Security and venting valves are not required for the patient&#39;s security during manual operation of the respiration bag because the gas chamber is in communication with the patient connecting piece via a control valve which alternately conducts exhaled gas to one end of a recirculation gas chamber or closes the communication to the recirculation gas chamber and conducts the exhaled gas from the gas chamber to the patient. The recirculation gas chamber, which holds at least the volume of gas exhaled by a mature person that has been in contact with the lung alveoli, is connected at its other end via a second check valve opening towards the respiratory gas receptacle, to the respiratory gas receptacle. A side duct, which is in communication with the atmosphere via the first check valve, is connected to the recirculation gas chamber near the one end, and a connection for supplying fresh gas from a pressurized source opens into the recirculation gas chamber immediately upstream from the second check valve.

BACKGROUND OF THE INVENTION

The object of the invention is to provide an anaesthesia-breathingapparatus by means of which gas can be supplied to a patient forartificial respiration, supported respiration, anaesthesia purposes orcombinations of such purposes. Such apparatuses which for example areknown from Swedish published specification 7308537-5 or U.S. Pat. Nos.3,814,091 and 3,901,230 comprises a gas chamber connected, on the onehand, to a patient connecting piece and, on the other hand, arespiratory gas receptacle, for example in the form of a respirationbag, a check valve adapted to permit discharge of excess gas from thebreathing apparatus to the atmosphere and, optionally, a filter forabsorption of carbon dioxide from recirculating breathing gas.

Most closely related with the object of the invention as far as thefunction is concerned is the anaesthesia-breathing apparatus accordingto the above-mentioned U.S. Pat. Nos. 3,814,091 and 3,901,230. Theapparatus shown fundamentally in FIG. 3 of U.S. Pat. No. 3,901,230operates substantially in the same way as the apparatus according to thepresent invention in those cases in which the patient is breathingspontaneously. Both apparatuses operate in this case according to thewell-known Magill-narcosis-breathing system. However, use of the knownapparatus is used for performing controlled ventilation, or supportedventilation which is a transition form between spontaneous respirationand controlled ventilation, the known has drawbacks which may bedangerous for the patient. In all the embodiments described in U.S. Pat.No. 3,901,230 a closure of the gas discharge valve can take place whenthe breathing bag is manually operated. If this happens the system isfilled with fresh gas causing the pressure to increase. For this reasonthe provision of a security valve in this system is required in order toprevent the build-up of dangerously high pressures in the lungs of thepatient in consequence of the gas supply. In addition the knownapparatus requires the provision of a venting valve which upon manualoperation permits discharge of gas from the excessively filled system topermit the state of locking to be removed.

SUMMARY OF THE INVENTION

Apparatus constructed in accordance with the present inventioncompletely removes these and other drawbacks by a construction in whichthe gas chamber is in connection with the patient connecting piece via acontrol valve which alternately conducts exhaled gas to one end of arecirculation gas chamber or closes the connection to the recirculationgas chamber and conducts the exhaled gas from the gas chamber to thepatient. The recirculation gas chamber, which at least holds the volumeof gas exhaled by a mature person that has been in contact with the lungalveoli, at its other end is connected, via a second check valve openingtowards the respiratory gas receptacle, to the respiratory gasreceptacle. A side duct, which is in connection with the atmosphere viaa first check valve, is connected to the recirculation gas chamber nearsaid one end, while a connection for supplying fresh air from apressurized source opens into the recirculation gas chamber immediatelyupstream from the second check valve.

If an apparatus having these characteristic features is used by apatient whose breathing function is paralyzed and which thus must besupplied controlled or at least supported ventilation, the control valveand the second check valve cooperate in such a way that during theinhalation phase, when the respiration bag is compressed, an independentrecirculation gas chamber is defined in such a way that the inflatingpressure cannot enter therein. As the fresh-gas supply and the firstcheck valve, i.e. the discharge valve, both are in connection with therecirculation gas chamber as defined, the following advantageousproperties which are not achievable with the apparatuses known so far,are obtained in the present apparatus:

1. No adjustment of the first check valve is required during transitionbetween spontaneous respiration and controlled ventilation(increased-pressure ventilation).

2. The supply of fresh gas cannot produce a pressure in the system inexcess of the opening pressure of the first check valve, that is,discharge valve.

3. The opening pressure of the discharge valve, i.e. the first checkvalve, can be chosen at a very low value.

4. Under no circumstances can an undesirable closure of the dischargevalve occur due to the flow conditions in the flow circuit or due to theoperation of the respiration bag.

5. The fresh gas can displace the alveolar expiration gas from thesystem not only during the last part of the exhalation phase after therespiration bag has become filled, but also during the whole inhalationphase. This means that the apparatus permits an "orderly" displacementof the alveolar expiration gas present in the recirculation gas chamberduring an extended period in comparison with the apparatus described inthe above-mentioned U.S. patent where only the last part of theexpiration period is disposable for this purpose. At a given adjustmentof the fresh-gas supply the apparatus according to the inventionaccordingly will displace alveolar gas at a highly increased efficiencywhich means improved fresh-gas economy.

In a particularly advantageous embodiment of the invention therecirculation gas chamber near the control valve has the shape of aconvergent-divergent duct, the side duct being connected to therecirculation gas chamber at the most constricted portion of theconvergent-divergent duct.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other embodiments of the object of the inventionas well as the operation of the apparatus are explained hereafter byreference to the attached drawings in which

FIGS. 1-4 schematically and in section show an embodiment of ananaesthesia-breathing apparatus according to the invention, FIG. 1showing the parts of the apparatus in the position corresponding to theinhalation phase, FIG. 2 in the position corresponding to the initialportion of the exhalation phase, FIG. 3 in the position corresponding tothe subsequent portion of the exhalation phase and FIG. 4 in theposition corresponding to the pause between inhalation and exhalation,

FIGS. 5 and 6 show in respectively longitudinal and transverse sectionschematically another embodiment of the anaesthesia-breathing apparatusaccording to the invention, and

FIG. 7 schematically and in section shows another embodiment of theanaesthesia-breathing apparatus according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the breathing apparatus according to FIGS. 1 to 4 the followingapparatus parts can be distinguished:

A gas chamber 1 occupying the interior of a corrugated flexible hose 2having stiff walls and rounded cross section is at the upstream end inopen communication with a filter 9 for the absorption of carbon dioxidefrom recirculating breathing gas, said filter in turn at the upstreamend being in communication with a conventional breathing bag 7 having anouter covering 8. It is to be noted that the filter 9 from a functionalpoint of view is not a necessary part of the apparatus and that theposition at which it is shown is not the only possible one.

At the downstream end the gas chamber 1 is in communication with apatient-connecting piece 3 via a control valve 4 which alternativelyconducts exhaled gas either to one end of a recirculation gas chamber 5or closes the communication to the recirculation gas chamber 5 andconducts the respiration gas from the gas chamber 1 to the patient.

The control valve 4 comprises a valve housing 4a having three connectionports 4b, 4c and 4d, port 4b leading to the gas chamber, port 4d intothe patient connecting piece 3 and port 4c into the recirculation gaschamber 5. A valve device 4e may assume different opening or closingpositions in cooperation with seats formed about ports 4b and 4c, valveelement 4e in the one position during supply of respiration gas to thefirst port closing the communication from valve housing 4a to the otherport 4c and simultaneously permitting the respiration gas supplied toflow via valve housing 4a to the third port 4d intended to communicatevia connecting piece 3 with the respiratory ducts of the patient. Whenthe pressure is discharged at the first port 4b valve device 4e isactuated by the pressure existing at the third port 4d due to a pressureincrease in the lungs of the patient, so that the first port 4 b isclosed and the exhaled gas is conducted through valve housing 4a fromthe third port 4d and out through the second part 4c.

In the same way as in gas chamber 1 the greater part of the wall of therecirculation gas chamber 5 consists of a corrugated flexible hose 6having stiff walls and rounded cross section. The chamber 5 at theupstream end is supplied with exhaled gas from the patient connectingpiece 3 through the control valve 4 as described above, whereas thechamber 5 at the other end is in open communication with a connection 12through which fresh gas is supplied from a pressurized source.

Close to control valve 4 the recirculation gas chamber 5 has the shapeof a convergent-divergent duct in the most restricted portion 13 ofwhich a side duct 11 is connected which at the opposite end is incommunication with the atmosphere via an outwardly opening check valve15.

At the end where the fresh-gas supply connection 12 opens into therecirculation gas chamber 5, chamber 5 is connected to the respiratorygas receptacle 7 or to the connection thereof with gas chamber 1. Acheck valve 10 opening towards the respiration gas receptacle, i.e. therespiration bag 7, is provided in the recirculation gas chamber 5immediately downstream from the connection 12 for supplying fresh gas.

The apparatus described above operates as follows:

During the inflation phase illustrated in FIG. 1 the respiration bag 7is compressed causing the check valve 10 to close the communicationbetween the respiration bag and the recirculation gas chamber 5 so thatgas from bag 7 flows through filter 9 and chamber 1 to the patientconnecting piece 3 through the control valve housing 4a in whichconditions are such that the communication with the recirculation gaschamber 5 is closed by valve device 4e.

During the expiration phase, i.e. during the patient's exhalation,exhalation air will initially flow from the patient connecting piece 3through the valve housing ports 4d and 4c into the recirculation gaschamber 5 while valve device 4e closes the communication with gaschamber 1 (FIG. 2). The exhalation gas, the greater part of whichinitially comprises unused gas, i.e. gas which has not been in contactwith the lung alveoli of the patient, enters into the recirculation gaschamber 5 and flows together with newly supplied gas from connection 12past check valve 10 into the respiration bag 7 which is in a stage ofexpansion. During the latter part of the expiration phase, after fillingof the respiration bag 7 and balancing of the pressure in this bag inrelation to the expiration pressure, the subsequently exhaled portion ofthe exhalation gas which predominantly comprises gas that has been incontact with the lung alveoli, will be discharged through side duct 11and check valve 15 to the extent this gas is prevented from entering therecirculation gas chamber 5 due to the presence therein of previouslyreceived exhalation gas together with fresh gas supplied from connection12. This latter part of the exhalation phase is illustrated in FIG. 3.

Finally, FIG. 4 shows the pause between the patient's exhalation and thesubsequent inhalation phase initiated by renewed compression of therespiration bag 7. During this pause exhalation air previously receivedin the recirculation gas chamber 5 will be displaced by fresh gassupplied from connection 12. The gas supply is so adjusted that the gasleaving the side duct 11 through check valve 15 entirely orpredominantly comprises used exhalation gas. From FIG. 1 it is seen thatduring the inhalation phase the expulsion of previously exhaled gas fromthe recirculation gas chamber 5 by fresh gas entering from connection 12will continue, the inflow through connection 2 obviously beingdimensioned in respect to the whole length of time during which therewill be no outflow of gas from the recirculation gas chamber 5 to therespiration bag 7, i.e. the latter part of the exhalation phase (FIG.3), the pause (FIG. 4) and the inhalation phase (FIG. 1).

In the construction according to FIGS. 5 and 6 a considerableconstructive simplification is obtained by exploiting the fact thatthree parallel flow ducts, the gas chamber 1, the recirculation gaschamber 5 and the side duct 11 may be combined in such a way that one ofthe ducts, in the case of FIGS. 5 and 6 the side duct 11, is bounded bya thin-walled flexible casing enclosing the two other ducts, in theexample shown gas chamber 1 and recirculation gas chamber 5, these twolatter chambers consisting of hoses 2 and 6 respectively that may becorrugated and which have stiff, but flexible walls. These adjacenthoses 2 and 6 deform the casing 14 to an oval cross sectional shape, thecavities formed between the outer surfaces of the hoses and the casingconstituting side duct 11 which connects recirculation gas chamber 5 viathe first check valve 15 with the atmosphere.

In analogy to the embodiment according to FIGS. 5 and 6 it is possiblethat gas chamber 1 and side duct 11 are hoses of rounded cross sectionhaving stiff but flexible walls, for example corrugated hoses, which areenclosed in a flexible casing 14 with a thin wall, said casing beingdeformed by the two enclosed hoses into an oval cross sectional shapeand connected in such a way with at least one of the enclosed ducts thatthe cavity formed between the outer surfaces of the hoses and the casingforms the recirculation gas chamber 5.

In the construction according to FIG. 7 the control valve 4 is connectedwith the patient connection piece 3 via a T-branch 18 and two extensionhoses 16 and 17 enabling the comparatively large control valve 4 to bemounted where it is stationary and spaced from the patient. In theembodiment according to FIG. 7 the control valve 4 comprises a housing4a having four communication ports 4b, 4c, 4f and 4g, out of which port4b communicates with gas chamber 1, port 4c communicates withrecirculation gas chamber 5 and ports 4f and 4g are respectively inletand outlet connections with the patient connection piece 3 via extensionhoses 16 and 17 respectively. The valve devices in the control valve 4comprise a directional valve (check valve) 4h and a bellows valve 4iwhich upon the supply of respiration gas to the first port 4b permitflow through port 4f while simultaneously the bellows valve 4i closescommunication from port 4g to port 4c. This condition is illustrated inFIG. 7. When the pressure in gas chamber 1 (and thereby in port 4b) isreleased the exhalation air (expiration gas) will be permitted to flowfrom port 4g outwardly through port 4c, while directional valve 4hcloses the communication in a backward direction from extension hose 16via port 4f. As for the rest, the embodiment according to FIG. 7 willoperate in the same way as the two previously described embodiments.

What we claim is:
 1. Anaesthesia-breathing apparatus for supplying gasto a patient, comprising:a first gas chamber having first and secondends; a second gas chamber having first and second ends, the first endof said second gas chamber being in the form of a convergent-divergentduct and the second end of said second gas chamber having an aperturetherein for introducing fresh gas from a pressurized source, said secondgas chamber holding a volume of gas which is at least equal to thevolume of gas exhaled by a mature person which has been in contact withthe lung alveoli; a side duct coupled to said second gas chamber at themost restricted portion of said convergent-divergent duct, said sideduct being provided with a first check valve for discharging excess gasto the atmosphere; a patient connecting piece; a control valve coupledto the first ends of said first and second gas chambers and to saidpatient connecting piece, said valve alternately conducting gas exhaledby said patient through said connecting piece to said second gas chamberor conducting a mixture of exhaled gas and fresh gas from said first gaschamber to said connecting piece, said control valve blocking the flowof exhaled gas into said second gas chamber when said gas mixture isbeing conducted to said connecting piece from said first gas chamber; arespirator gas receptacle connected to the second ends of said first andsecond gas chambers; and a second check valve positioned in said secondgas chamber between said aperture for introducing fresh gas and saidrespirator gas receptacle, said second check valve opening toward saidrespirator gas receptacle.
 2. Anaesthesia-breathing apparatus as claimedin claim 1 wherein said control valve comprises a housing, first, secondand third connection ports and a valve device, said first and secondconnection ports being coupled to the first ends of said first andsecond gas chambers respectively and said third connection port beingcoupled to said patient connecting piece, said valve device permitting aflow of gas under pressure from said first port to said third port whileclosing off communication from said housing to said second port, and,upon release of the pressure at said first port and an increase inpressure at said third port, closing said first port and permitting aflow of exhalation gas from said third port through said housing to saidsecond port, the pressure at said third port resulting from a pressureincrease in the lungs of the patient.
 3. Anaesthesia-breathing apparatusas claimed in claim 1 wherein said first and second gas chambers arefirst and second flexible corregated hoses respectively having stiffwalls and a rounded cross-section, and wherein said apparatus furthercomprises a thin-walled flexible casing surrounding said first andsecond hoses, said casing being deformed by said first and secondenclosed hoses into an oval cross-sectional shape, the space between theouter surfaces of said hoses and the inner surface of said casingforming said side duct.
 4. Anaesthesia-breathing apparatus as claimed inclaim 1 wherein said first gas chamber and said side duct are first andsecond flexible corregated hoses respectively having stiff walls and arounded cross-section, and wherein said apparatus further comprises athin-walled flexible casing surrounding said first and second hoses,said casing being deformed by said first and second enclosed hoses intoan oval cross-sectional shape, the space between the outer surfaces ofsaid hoses and the inner surface of said casing forming said second gaschamber.
 5. Anaesthesia-breathing apparatus as claimed in claim 1wherein said control valve comprises a housing, first, second, third andfourth connection ports and first and second valve devices, said firstand second connection ports being coupled to the first ends of saidfirst and second gas chambers respectively and said third and fourthconnection ports being coupled to said patient connecting piece, saidfirst valve device opening to permit flow of gas under pressure fromsaid first port to said third port while said second valve device closesoff communication from said housing to said second port, and, uponrelease of the pressure at said first port and an increase in pressureat said third and fourth ports, said first valve device closes saidthird port while said second valve device opens to permit flow ofexhalation gas from said fourth port through said housing to said secondport, the pressure at said third and fourth ports resulting from thepressure increase in the lungs of the patient.
 6. Anaesthesia-breathingapparatus as claimed in claim 5 which further comprises first and secondextension hoses each having first and second ends, the first ends ofsaid hoses being coupled to the third and fourth ports of said controlvalve respectively; and a T-shaped member having first and second armscoupled to the second ends of said first and second extension hoses anda third arm coupled to said patient connection piece, said extensionarms allowing said control valve to be stationarily mounted at adistance from the patient.
 7. Anaesthesia-breathing apparatus as claimedin claim 6 wherein said first valve device comprises a directional valvemounted in said third port and said second valve devices comprises abellows valve mounted between said fourth and second ports, the openingand closing of said second valve device depending on the pressure insaid first port and in said second extension hose. 8.Anaesthesia-breathing apparatus as claimed in claim 1 which furthercomprises a filter in series with said first gas chamber, said filterabsorbing carbon dioxide from recirculating breathing gas.